1. Technical Field
The disclosure relates to a method of manufacturing a shell, more particularly to a method of manufacturing a plastic shell.
2. Description of Related Art
The appearance design of a case of an electrical product has become one of some considerations that consumers would pay attention to or purchase. In view of that, manufacturers dedicate to provide many kinds of electrical products featuring distinguished appearances or styles one after another. One of the common ways to provide the electrical products with distinguished appearances is to present colored patterns printed on the case thereof by using inked color paint, so that consumers who are used to pursuing products with novelty and fashion appearances would be interested and motivated to purchase one of them.
In addition, in order to massively manufacture the cases of the electrical products and satisfy a demand of convenience to carry for users, the cases of the electrical products are normally made of plastic materials by injection molding. After an case thereof is formed by injection molding, the case will be further sequentially processed by a colored primer coating step, an inked pattern printing step and a UV lacquer painting step to provide an exterior hard layer on the case.
However, organic solvents must be used a lot in the colored primer coating step and the inked pattern printing step, and some drawbacks will be happened while putting plastic materials and organic solvents together.
When a plastic material is characterized with highly chemoresistance from the organic solvents, the organic solvents in the inked color paint is not easy to unite with the plastic material, thus, the inked color paint will be difficult to stay on an case having the plastic material, even the inked color paint will be easily peeled from the case.
Contrarily, when another plastic material is characterized with low chemoresistance from the organic solvents, the plastic material would be eroded by the organic solvents, so that cases having the plastic material might be cracked or damaged seriously, as a result, the defective rate of the cases is increased.
Furthermore, since some paint products has some ingredients (e.g. Halogen or heavy metals) which are unable to recycle completely or possible to endanger the local environment, the paint products will be restricted to use or sell in some business trading areas or countries.
Recently, a technology of “In-Mold Roller” (IMR) is provided in production of cases of the electrical products. Before plastic material is injected into a mold of injection molding, an IMR film with inked patterns is provided between two separated dies of the mold. When the dies are closed together, the plastic material is liquefied and injected into the mold. After that, when the plastic material in the mold is formed and solidified, the inked patterns of the IMR film are transferred to print on it, so as to form a plastic case with inked patterns printed thereon.
Refer to FIG. 1 in which FIG. 1 is a schematic view of an IMR film to process the IMR procedure. The IMR film 200 includes a base film layer 210 (or called release film) and some transferable pattern units 220 equidistantly arranged on one surface of the base film layer 210. Each of the transferable pattern units 220 comprises a hard coating layer 221, an inked layer 230 and an adhering layer 240 sequentially stacked up on the base film layer 210. The inked layer 230 has at least one pattern composed with inks or paints.
When the dies mentioned above are closed together to clip one of the transferable pattern units 220 between the dies thereof, the liquefied plastic material is injected into the mold to directly encounter the adhering layer 240. When the plastic material is cooled and formed into a solidified case 250, the transferable pattern unit 220 is bonded on the solidified case by the adhering layer 240. After the solidified case 250 is rejected from the mold, the inked layer 230 can be observed as printed on the solidified case 250. Thus, the solidified case 250 with color patterns might provide features of artistic and identification.
However, the procedure of fabricating the IMR films 200 needs to make an electroformed printing plate with relevant patterns thereon in advance, and using the electroformed printing plate to print the patterns with ink on the base film layer 210 then. Therefore, since the procedure of fabricating the IMR films 200 is quite complicated, time consuming and labor intensive, the cost is high, so massive production has to be conducted to proportioning the fabrication cost to each finished product.
Furthermore, for a small-amount production or for customized products, the average selling price (ASP) cannot be lowered if the quantity of the IMR film fabrication is a small number. Thus; it will be a challenge to be overcome for the manufacturers.